SURFACE MODELS FOR GAMMA-AL2O3 FROM MOLECULAR-DYNAMICS SIMULATIONS

Molecular dynamics simulations for gamma-Al2O3 and La3+-doped gamma-Al 2O3 crystals have been performed. From bulk simulations a description of the crystal-terminating layers in both doped and pure alumina solid s is reported. The molecular dynamics simulations allow us to describe systematically for the first time the surface of the gamma-Al2O3 crys tal, taking into account the actual stoichiometry of the solid. This d escription results in a model in which the number of different surface sites is increased with respect to the previously reported models. Th e number of different surface sites may account for the IR spectra of hydroxy groups adsorbed on gamma-Al2O3.